Dispersions containing solid dispersible particles, such as organic or inorganic pigments and fillers, and polymer additives, namely dispersants, are used in an almost unlimited number of different technical applications, e.g. as coating materials, for printing inks, colouring plastic materials, including fibres, glasses, or ceramic products, for formulations in cosmetics, or for the preparation of paint systems, in particular automotive, industrial and decorative paints.
The function of polymeric dispersant in such dispersions is manifold. Mainly, they act as stabilizers for the solid fine particulate materials, i.e. the dispersant separates the particles of the solid fine particulate material and thus prevents them from coagulation or clumping and settling from the liquid phase. They also may act as solubilisers in the given carrier liquid, e.g. water or organic solvents. Polymer additives may also improve the gloss of the dispersion or enhance its rheology. Depending on the type and polarity of the dispersing agent, e.g. water, organic solvents or mixtures thereof, polymers of variable structures are chosen. In view of ecological requirements, the use of aqueous pigment dispersions is particularly preferred, as well as dispersions based on organic solvents with high solids content.
In view of the almost unlimited range of different technical applications, there remains a growing need for dispersants of improved pigment affinity and rheology behaviour, as expressed by the viscosity of the mill base at a given shear rate and improved gloss of surface coatings.
WO 92/13911A1 relates to acetoacetanilide functionalized poly(alkylene glycol)s which are prepared by reacting a poly(alkylene glycol)monoamine, diamine or triamine with isatoic anhydride followed by acetoacetylation of the resultant aminobenzamide. WO 92/13911A1 suggests using said acetoacetanilide functionalized poly(alkylene glycol)s for preparing improved diarylide pigment compositions which, in turn, are useful for preparing storage stable printing inks, especially of the publication gravure type inks.
Occasionally, the use of comb copolymers, in particular those based on styrene and maleic anhydride (so called SMA resins), as wetting and dispersing agents for pigment and filler dispersions, has been described. The backbone of said comb polymers is usually designed as anchoring groups which have affinity onto the solid particle surface and thereby provide a strong physical binding of the dispersant to the solid particles. Their side chains can interact with the dispersant phase to build up a steric environment to stabilize particle dispersion.
WO 2002/051948 describes pigment dispersants which are comb polymers obtained by polymerizing an acrylate monomer, a vinylaromatic hydrocarbon monomer, a non-functional polyalkylene glycol acrylate or methacrylate monomer and a functional polyalkylene glycol acrylate or methacrylate monomer having a hydroxyl group subsequently reacting the thus obtained comb polymer with an acid having a first functional acid group reactive with said hydroxyl group, and a second functional acid group capable of providing an acid anion group.
WO 2007/039603 describes a pigment dispersant which is a comb polymer having pendent hydrophilic polyalkylene oxide side chains which are obtained e.g. by reacting an SMA type polymer with a polyalkyleneoxide amine.
WO 2008/080580 describes modified comb copolymers based on SMA resins and their use as wetting and dispersing agents, where the comb copolymers are obtained by converting SMA resins with one of the following mixtures (a) to (c), where (a) is mixture of at least one polyalkylene oxide monoamine and at least one amino alcohol; (b) is a mixture of at least one polyalkylene oxide monoamine and at least one N,N-disubstituted diamine, (c) is a mixture of at least one polyalkylene oxide monoamine, at least one N,N-disubstituted diamine and at least one polymer selected from the group of monohydroxy-terminated polyalkylene oxides, monohydroxy-terminated polyesters and monohydroxy-terminated block copolymers comprising polyalkylene oxide and polyester blocks. These comb copolymers may be further modified by converting the hydroxy-terminated side chains to phosphoric acid ester groups or by converting N,N-disubstituted aminoterminated side chains to quaternary ammonium salts.
The earlier filed international patent application PCT/IB2013/051454 describes polymers having pending anthranilate or anthranilamide groups which may be attached directly or via a bivalent spacer to the polymer back-bone or to the termini of the polymers and their use as pigment dispersants.